LibertyCommerceInternational handles many types of discount.
A fixed discount given to one customer can be specified through settings for customer supplier information. If this option is active, all products for a specific customer will be discounted by a fixed rate.
Discounts can also be specified on a per-invoice basis whenever
entering an invoice. This bypasses the selected price list and allows one
to specify a discount rate for each item.
NOTE: if a discount is specified for a product, the discount will be repeated for all other items in an invoice to facilitate entering a fixed discount rate. If this rate is changed, then the programme will not repeat it any more.